[NET]: DIV_ROUND_UP cleanup (part two)

Hopefully captured all single statement cases under net/. I'm
not too sure if there is some policy about #includes that are
"guaranteed" (ie., in the current tree) to be available through
some other #included header, so I just added linux/kernel.h to
each changed file that didn't #include it previously.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index 60112bc..14f0c88 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -64,7 +64,7 @@
 {
 	unsigned long ticks = ntohs(get_unaligned((__be16 *)src));
 
-	return (ticks * HZ + STP_HZ - 1) / STP_HZ;
+	return DIV_ROUND_UP(ticks * HZ, STP_HZ);
 }
 
 /* called under bridge lock */